saltform

Saltform refers to the salt form of a chemical compound, created when an acid–base reaction converts a neutral molecule into ionic species. In this context, a cation usually arises from a basic site such as an amine, while an anion comes from an acid such as chloride, sulfate, or citrate. The resulting salt form is often pursued to alter physical properties without changing the core chemical structure.

Formation of a salt form typically involves reacting the base with an acid or exchanging counterions in solution. Common examples include amine hydrochloride salts (RNH3+ Cl−) and carboxylate salts (RCOO− with a counterion such as Na+ or K+). Salt formation can also occur through interaction with organic acids to give organic acid salts, or with inorganic acids for inorganic salt variants.

In pharmaceutical settings, salt forms are selected to improve properties such as solubility, dissolution rate, stability, hygroscopicity, and manufacturability. Salt forms can influence bioavailability and pharmacokinetics, though they do not change the drug’s active moiety. Often multiple salt forms exist for a single active pharmaceutical ingredient (API), each with distinct handling and performance characteristics. Salt formation is reversible under certain conditions, such as changes in pH or exposure to moisture, which can lead to deprotonation or exchange of counterions.

Characterization and regulation of salt forms involve identifying the counterion, assessing solubility and stability, and ensuring appropriate labeling. Naming conventions typically specify the counterion (for example, hydrochloride, sulfate), and regulatory guidelines require clear specification of the salt form used in a product.